Proceedings Paper

Generation of thermal donors (TDs) and oxgen precipitation as a result of low tiperature annealing of boron-doped CZ-silicon under nitrogen axibient for different durations has been studied by resistivity and FTIR measurements. Donor generation rate is very rapid in the early stage of annealing and decreases later on. Prolonged annealing accelerates the process of oxygen precipitation yielding a maxiniim value of 1.97 ppme for 187 hrs. of annealing. The oxygen redu ct ion can be described by the second order kinet ics . Thermal diffusion coefficient has been estimated to be 5.52x1O' cm s and activation energy 1.089 eV. CZsilicon samples with high and mederat initial oxygen concentrations have also been annealed in air-ambient at 450 C and analysed the effect of oxygen and carbon in all the cases. Arnbients do not appear to affect the TD genera t ion kinet i Cs . The resu 1 ts of the inf luence of oxygen and carbon on donors generated by annealing at 6500C for 100 hrs in the two CZ-Si samples with initial oxygen concentration 33.5 and 34.5 ppma and carbon concentrations 1.5 and 1.0 ppma respectively, and the donors so generated as a function of oxygen and carbon reduction due to precipitation are presented and discussed. Controversial issue of the exact nuirber of oxygen atoms involved in a TD formation is debatable in view of the divergent estimates put forth by the workers. Involvement of 7-0. atms in a single TD sounds mere logical as also opined by Lindstrcm et1al. because thermal treatment creates a self-.insterstitial (Si1) and Si1 so created is surrounded by six O.-atons which become mere mobile as a result of increase in temperature. bne occupies the site vacated by silicon atom. One single TD may contain maxinum 7 nearest 0. atoms with Si as a nuclais.